Attrition mill



Nov. 12,` 1940. y 1w. vH. P. BOLL *12,221,176

ATTRITIQN MILL Y v Filed March 28, 1938 2 sheets-sheet A1 /WM/ffa Y 42% Patented Nov'. 1940 ,AI'IRITIONMILLLZ n Y William Hubert Paul Boll, Sydney, Australia, L

Appiicmii Marcil 2s, 1938, sensi No.`1 9s,31

. j In Australia June 12 v1937 1i claiml (ci. ,s3- 9),-

,This invention relates to rotary'grinding orV attritionk mills, for thepreliminary reduction of substances, or the grinding or attrition thereof, or the intimate,blending of two or morefsubstances.' i,

The principal vobject of the invention is vto provide a rotary mill which will grind substances to a finer and more uniform degreeforwhich will cause a more intimate blending of two or ljmore substances, than is possible" witlrmills hitherto employed. l 1 ,y v

The mill-according to theinventionincludes a chamber of cube shape, containing a yplurality of A ll lopposed Vcorners for rotation in suitablebearings.

The mill may be used for the treatment of varipolished balls, which is mounted by its diagonally ous substances, such as metal-bearing ores,"'grain,

- moulding powders, and others.

E For use in grinding or mixing 'nner materials,

such as-moulding powders or rice for cosmetic f purposes, ythe grinding or mixing may be carried I For heavier materials, such4 as on in batches. metal-bearing ores, but. also forl ne materials,

Vthe materialis charged and yf lischargedKeither y continuously or in batches),throughl feed and A discharge tubes enteringit throughthe chambery This continuous removal ofmmilled bearings. n l material, during grinding, facilitates th'egrind- Ming. of thematerialvr'emaining' the chambeigf.`

- andrenderslthe mill particularlyjefllcient.

They milling chamber yis ofcube shape, and (in v account of V its particular, mounting with .the

diagonally opposed cornersof the .chamberv (as f distinguished from the diagonallyoppositecorners of any one side) disposed'in its axis of rotay tion, thematerial and the. balls therein followan A unusualpath4 and set up a novel and effective grinding operation. As the' chamberlrevolves in 40 its bearings, the various corners thereof ',(other than the corners held in the bearings)"a"ssu`me the lowest position in succession, and the balls and the material are continually sliding down one or more sides of the chamber towards ythe instantaneously lowest point, repeatedly changing their direction during each rotation of the chamber. The contents generally slide, across the width and length of the chamber, in streams which cross and recross and intermingle in a manner resulting in a complete intermixture or grinding of the material(s)'. The reduction of 'the material, and/or the intermixture of two or more materials, is caused by the constant. frictional movement of the particles over each other. The polished steel balls are not for the purpose bearing of the milling chamber of Fig. 1; andthe of pulveris'ing b'yimpact, but are` for the'purpose kof adding tol the" weight' of the mass, and causing it to ,slide freely over the interiorllof lthe' chamber during rotation. y

After the chamber has been'imnotionfor ya s few'cycles', the 4materialand the balls aredistributedgenerally around theiinterior rof the chamber, and consequently the `mill is subv stantially balanced. l Owing to this fact, thepower required to keepthe mill in rotation isparticul0 In order to .fully describe the invention reference is made Ato the"faccompanying drawings,in

chamber and bearings,V f V cork, straw, silica, pulp, lceramic materials.

Fig.'2 is across-sectional elevation of oneendk feed thereto,

3vr is -a.'cross'sectional elevation of the other end bearing; vand thedischarge means;

f Fig.v '4His an enlarged vertical section on line Fig. 5 is an enlarged v"'viewv'o'f the bearing of 25 The hollowmilling chamber 8 is of cube form,

which 'is mounted by-its diagonally 'opposite corners., 9, 9 l(as.l distinguished from the diagonally oppgsitefcornerswof anyone side) in expansion r'30 bearings I0, I0. 'I'hebearing Il)`rv at either `side is the sanie, and'is illustrated in'Figs.=-2"3, 4 and 5. Thebearing lat theIeed-side ofi-the milljis formed about a' feedA tube I I Asecured in `a pedestal I2, andthe'bearing IIIatthe-dischargegg n vside ofthe tube' is formed about a discharge tube I3 mounted in apedestal'll. f l n v Each bearing I0 comprises-atapered collar VI5 formedabout the tube II-for tube I3) "and uponlwhich ya ball race I6 i'sclampe'd by a vringV 40 nut I'I threaded on thetube. LThe rolling (outer) jring vlszqzif thef'ball 'race I6 ycarriesfkan'annular 'sleeve I9int`o which an-inner closure disc 20 and an outer closure disc 2'I are pressed." A s shown in Fig. 5, the closure disc 2l .may be secured to 45 the sleeve I 9 byvset screws 22, 22. Thus it will.

be observed that the outer ring I8 of the ball race, the sleeve I9 Yand the closure discs 20 and 2| revolve on the ball race I6 about the tube Il (or the tube I3). 50'

Sleevev I9 is formed with four symmetrically spaced longitudinal grooves, 23, 23 (Figs. 4 and 5) in'its outer periphery, to form a seating for a plurality of balls 24, 24.

Y Each mounting corner 9 of the chamber 3 isl 55" lformed with a hollow bearing sleeve 25 which is an easy tit over the sleeve I9. The inner surface of sleeve 25 is formed with four longitudinal grooves 28. 28 (Figs. 4 and 5) which register with grooves 23, 23 and which receive the balls 24, 24, as shown in Fig. 4. By means of the balls 24 mounted between the registering grooves 23 and 28 of the sleeves I9 and 25 respectively, the sleeve 25 is constrained to rotate with sleeve I9, but it may slide axially thereon to permit expansion of the millingchamber 8 due to the heat engendered in milling.

The outer surface of each sleeve 25 is -tted with four equally spaced blocks 21, 2`I secured by set screws 28, and to these blocks two spaced sprockets 29, 29 are secured by'setv screws30.

Feed tube I I (Fig. 2) communicates with a feed pipe 3I through which the material to be milled is fed. A helical screw conveyor 32, formed about'A a hollow shaft 33, extends'from below pipe 3I and through feed` tube II, Shaft'33extends from s pedestal .I2 and is carried in two spacedbearings 34 and 35, between which the shaft is tted with a driving sprocket 38 by means of which it-is rotated. Externally of bearing 34 the shaft is connectedkby means of a rotatable coupling`3l with an air supply pipe 38. The inner end of hollow shaft 33 (within chamber 8) is fitted with a spray head 39.`

'I'he discharge tube I3 is internally formed as a Venturi tube 40 (Fig. 3) and it communicates with a delivery pipe 4I mounted on pedestal I4.

The milling chamber 8 isv provided with a number of polished steel balls 42, 42 (Fig. 1)k and access to the interior. of the chamber is had through any suitable detachable door 43.

The operation of the mill isasfollows:

The material (or materials) to bemilled, either by way` of attrition or intermixture, or both, is fed through pipe 3|, and conveyor shaft33 is revolved fromy sprocket 36 to convey this material through feed tube II and into milling chamber 8.

v.This feeding of the material into 'the milling chamber may be continuous or intermittent, and it may occur with the chamber 8 in rotation or stationary. y

Thel millingy chamber 8 is revolved ,from a `.source of power through chains reeved about sprockets 29, 29 and during the rotation of the chamber the various, cornersthereof (other than l. the pivot corners 9, 9) assume in succession the instantaneouslylowest position,`causing the materialandbalis to follow. an unusual path resulting in a novel and effective grinding operation.

. The balls .42 cause the material to freely vand continuously cascade over the interior surfaces of the chamber towards the instantaneously. lowest corner in separate streams which crossand recross and intermingle with each other. This peculiar movement of the material causes a high degree of vfrictlonal movement of the particles of the material over each other, which frictional movement results in particularly ne grinding y of the material recovered can be exercised by varying the pressure of the compressed air. Where metal-bearing ores are being treated, fine metal particles deposited in the downward slop- `ing bore 48 of tube I3 are returned to the cham- 'ber 8 by the natural vibration of the mill. 'I'he continuous removal of milled material facilitates the eillcient grinding of the remaining material.

Expansion of chamber 8, due tothe heat engendered by milling, is made possible by the axial displacementof the sleeves 25 on the balls 24 which also permits the chamber to effect its natural axial vibration. The material remaining in chamber 8 after milling is completed, togethery ,with balls' l42, are removed through detachable door 43. I

The invention yprovides a mill which will, owing to its peculiar action, perform-'the reduction or intermixture vof materials toa. degree hitherto lunobtainable in a mill, and moreover'provides a mill which has an extremely long life and which requires but a fraction of the power usually taken by ball mills. The mill'also reducesthe material to a particularly uniform degree lof tlrieness. I claim: A l A` mill comprising a rotatable cube-shaped chamber supported at two 'diagonally opposite corners, a plurality of grinding balls in vsaid rotate and individual corners of the'chamberI to Aassume in successionV the instantaneously lowest position and the balls to roll during each rotation to such instantaneously lowest corners of the` sleeve, and longitudinally extending ball races disposed in registering grooves of both sleeves, which ball racesv constrain the sleeves to rotate with ,one another but permit their relative 'axial 'displatement4 l e WILLIAM PAUL BOLL.

chamber, driving means causing the chamber to 

